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Microbiology and Immunology
MCIM 326
Sydney Hayes

BacteriophagePhage predominant form of genetic biomass on earthvirus that infect bact can be symbiotic Microbiome all microorg communities that share our body spacecan weigh as much as brain most abundant species in large intestines Phage MorphologiesI Polyhedral bare head spiked head tailedII FilamentousIII Enveloped Phage GenomesssDNA circular dsDNA circular or linear ssRNAdsRNAHighly diverse morphology in environment without eukaryotic competitorsHigh phagetobacterium ratio Nomenclature all prefixes end with viridaeCubicmicro levi cysto cortico dsDNA circularTailedmyoviridaestylo pedo Filamentous ino ssDNAAlso pleomorphic varying shape Pilusdependent Phage Infection NonlyticFf phages filamentous phagestotal dependence on Fpilus for infectionInfect by attaching to F pilus made by F plasmid M13 phage attaches to tip of F pilus of E coli Genome existsIn ssDNA form inside phage onlystrand rep made from RF replicative formIn ds RF within cell nicked or cccDNARF DNA circle can be transformed to host cellproduce filamentous phage isolated in plaques M13 phage Circular ssDNA packed into tube coated in major coat protein pVIIIminor protein pIII at endsbind to F pilusNonlytic life cyclestrand leaves cell wall without lysing picking up capsid phage coat protein pVIII in inner CMstrand is coated with gpV ssDNA binding protein as it peels off from rc replicationgpVIII binds IM and faces periplasmic space cleavesreplaces gpV as virus extruded from cellFf phages cont extrude from host cell envelope Phage assembly coupled with exportpV coatsssDNDpVIII on IM replaces pVMore protein interactionsComplex released from IMleaves cellTargets new cellRC replicationIn target cellss genome replicated bystrand replication to form ds RF ssDNA contains hairpin structure that recruits RNA polymerase for primerinitiate replicationIGIntergenic Region includes bothstrand ori of rephairpin structureProteinscoded onstrand of ds RF templateIn RF template Gene II endonuclease nicksstrand origincovalently bond to 5 end exposing 3 OH endRC rep ofstrandstrand is peeled off strand packaged in phagePhagemids can be replicated as plasmidsfilamentous phage ssDNA propertiesContains ColE ori of plasmid rep selectable marker resistance major IG region of filamentous phageOccurs when cellphagemid is infected with helper gene containing gene II of M13 gpII interacts with IGRCstrand rep to produce phagemid plasmidssDNA RC rep used for foreign DNA analysis site directed mutagenesis strandspecific hybridization probPhagemids provide 1 high yield of ds plasmid DNA 2 eliminate the need to subclone DNA fragments from plasmids to filamentous phageNonPilusDependent Phage Infection phage attachment site on cell bound by
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